rootless does not follow symlink to /run/netconfig/resolv.conf

Description

In the rootless context docker does not follow symlinks from /var/run to /run.
When /etc/resolv.conf is linked to /var/run/netconfig/resolv.conf, and a link exists from /var/run to /run, DNS resolution fails in the rootless context. It uses the slirip4netns fallback nameserver running on 10.0.2.3.

It works fully well with the default context (daemon running as root), and with /etc/resolv.conf linked to /run/netconfig/resolv.conf in rootless.

The most likely source of the /var/run/netconfig/resolv.conf symlink is that my server was upgraded from SLES 12 to SLES 15 some years go.

If anyone stumbles upon this: try linking your /etc/resolv.conf to /run/netconfig/resolv.conf:
ln -s /run/netconfig/resolv.conf /etc/resolv.conf

Reproduce

1. sudo rm /etc/resolv.conf
2. ln -s /var/run/netconfig/resolv.conf /etc/resolv.conf
3. docker pull or docker login registry.example.com
4. you will get a timeout since registry.example.com cannot be resolved by slirp4netns local dns

Expected behavior

dns resolution should work fine when /var is linked to /run

docker version

client 28.5.1-ce
api 1.51
go 1.24.10
containerd 1.7.29
runc 1.3.4
slirp4netns 1.2.2

docker info

Unfortunately I cannot post this, since the bug happened on my company machine

Additional Info

No response

Start by tracing Docker's rootless DNS and resolv.conf handling, especially where the slirp4netns fallback nameserver is selected. Reproduce the setup with /etc/resolv.conf pointing through /var/run to /run, then verify that registry.example.com resolves without falling back to 10.0.2.3.